Sensory information about the external world reaches the cerebral cortex through the thalamus. For each sensory system a `primary' thalamic nucleus transmits information from the periphery to primary sensory cortices, and a `higher-order' thalamic nucleus further links distinct cortical areas via reciprocal connections with primary and associational cortices. Here, our overall goal is obtain a better understanding of how higher-order thalamic nuclei contribute to sensory processing. We will accomplish this by utilizing a well-characterized and genetically tractable model system, the mouse whisker- barrel system. In mice, the posteromedial (POm) thalamic nucleus is the higher-order thalamic nucleus for the somatosensory system and links primary somatosensory cortex (S1) with motor cortex other associational cortices through a `cortico-thalamo-cortical' pathway. This pathway is thought to play a direct role in sensorimotor behaviors, however its function has never directly been tested in an awake behaving animal. In this proposal, using a combination of electrophysiological recordings, optogenetics, and behavioral paradigms our objective is to determine whether POm is required for the perception of somatosensory stimuli during basic whisker-dependent behavioral tasks. We hypothesize that POm neurons may preferentially respond to somatosensory stimuli that are behaviorally salient to the animal, making it necessary for even simple somatosensory tasks. This may be due to a role in attention, as opposed being involved strictly in stimulus representation, and could serve to enhance cortical activity to behaviorally relevant stimuli.